Because of their light weight, small diameter, low transmission loss and large transmission capacity, optical fiber cables have potential use as marine cables under high water pressure conditions. A construction wherein a bundle of coated optical fibers is confined in a pressure container such as a metal tube to protect them from an external force has been proposed as an optical fiber cable adapted for use under high water pressure. However, an undersea cable that is laid down on a sea bed which may be several thousand meters deep must withstand a water pressure of several hundred kg/cm.sup.2. To meet this requirement, the wall thickness of a pressure container such as a metal tube must be increased appreciably, but with the present level of manufacturing technology, the production of such pressure container is very difficult. To eliminate this problem, a cable of the construction shown in FIG. 1 has been proposed; the cable comprises an airtight tube 01 which has both a bundle of coated optical fibers 02 and fluid 03 so that the pressure inside the tube 01 is equal to the pressure outside the tube when the tube is placed under high pressure. However, when an external force is applied to this type of cable, the fibers 02 undergo microbending that increases transmission loss. In addition, the cable is not satisfactorily protected from external forces whereby problems such as breakage of fibers may occur.